In comparison to noble metals (gold and silver), aluminum is a sustainable and widely applicable plasmonic material owing to its abundance in the Earth’s crust and compatibility with the complementary metal–oxide–semiconductor (CMOS) technology for integrated devices. Aluminum (Al) has a superior performance in the ultraviolet (UV) regime with the lowest material loss and good performance in the full visible regime. Furthermore, aluminum films can remain very stable in ambient environment due to the formation of surface native oxide (alumina) acting as a passivation layer. In this work, we develop an epitaxial growth technique for forming atomically smooth aluminum films on transparent c-plane (0001) sapphire (Al-on-Sapphire, ALOSA) by molecular-beam epitaxy (MBE). The MBE-grown ALOSA films have small plasmonic losses and enable us to fabricate and utilize high-quality plasmonic nanostructures in a variety of optical configurations (reflection, transmission, and scattering). Here, the surface roughness and crystal orientation of ALOSA films are characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). Moreover, the formation of smooth native oxide layer and abrupt heterointerfaces are investigated by transmission electron microscopy (TEM). We have also measured the optical dielectric function of epitaxial aluminum films by using spectroscopic ellipsometry (SE). These results show that the structural and optical properties of epitaxial aluminum films grown by MBE are excellent compared to polycrystalline aluminum films grown by other deposition methods. To illustrate the capability of device applications for the full visible spectrum, we demonstrate clear surface plasmon polarition (SPP) interference patterns using a series of double-groove surface interferometer structures with varied groove–groove separations under white-light illumination. Finally, we show the device performance of zinc oxide (ZnO) nanowire (UV) and indium gallium nitride (InGaN) nanorod (blue and green) plasmonic lasers prepared by using the epitaxial Al films. The measured lasing thresholds are comparable with the best available data obtained on the Ag films. According to these result, we suggest that epitaxial ALOSA films are a versatile plasmonic material platform in the UV and full visible spectral regions.

中文翻译：

---

外延蓝宝石铝膜作为紫外线和全可见光谱区域的等离子体材料平台。

与贵金属（金和银）相比，铝是一种可持续发展且广泛应用的等离子体材料，因为铝在地壳中含量丰富，并且与用于集成设备的互补金属氧化物半导体（CMOS）技术兼容。铝（Al）在紫外线（UV）方面具有优异的性能，而材料损失最少，在全可见光范围内的性能也很好。此外，由于形成了用作钝化层的表面天然氧化物（氧化铝），铝膜在周围环境中可以保持非常稳定。在这项工作中，我们开发了一种外延生长技术，用于在透明c上形成原子光滑的铝膜。分子束外延（MBE）制成的平面（0001）蓝宝石（Al-on-Sapphire，ALOSA）。MBE生长的ALOSA薄膜的等离子体损耗小，使我们能够制造和利用各种光学配置（反射，透射和散射）中的高质量等离子体纳米结构。在此，ALOSA膜的表面粗糙度和晶体取向通过原子力显微镜（AFM）和X射线衍射（XRD）表征。此外，通过透射电子显微镜（TEM）研究了光滑的天然氧化物层和陡峭的异质界面的形成。我们还通过光谱椭圆偏振法（SE）测量了外延铝膜的光学介电功能。这些结果表明，与通过其他沉积方法生长的多晶铝膜相比，通过MBE生长的外延铝膜的结构和光学性能优异。为了说明设备应用在全可见光谱范围内的能力，我们使用了一系列双凹槽表面干涉仪结构，在白光照射下具有变化的凹槽-凹槽间隔，展示了清晰的表面等离子体激元极化（SPP）干涉图样。最后，我们展示了通过使用外延Al膜制备的氧化锌（ZnO）纳米线（UV）和氮化铟镓（InGaN）纳米棒（蓝色和绿色）等离子体激元激光器的器件性能。测得的激光阈值可与在Ag膜上获得的最佳可用数据相媲美。根据这些结果，